1. Field of the Invention
This invention relates to a lumped constant delay line comprising an inductance element and capacitors connected together, and more particularly relates to a subminiature ultrahigh speed delay line having a fast rise time and suitable for digital circuits of computers, etc.
2. Description of the Prior Art
Until now, delay lines formed by cutting a coaxial cable to a suitable length to obtain a desired delay time, and microstrip lines which can be considered as distributed constant lines, etc., as shown in, for example, U.S. Pat. Nos. 3,585,534 and 3,585,535, have been proposed as delay lines having fast rise times, for example 1 nS or less.
However, in the former case the size of the line is large and terminal processing is troublesome, and in the latter case the size is large, the cost is high and the characteristics are undesirable.
On the other hand, a lumped constant delay line formed by connecting capacitors and a plurality of inductors wound on a bobbin has been employed. However, with such a lumped constant delay line it is difficult to achieve optimum coupling between the inductors at high frequencies, for example at frequencies above 1 GHz, and hence it was considered difficult to achieve a rise time of less than 1 nS.
Accordingly, the conventional lumped constant delay line had the disadvantage that a rise time of less than 1 nS could not be achieved because the delay characteristic degraded at high frequencies. Under these circumstances, the coaxial cable, etc. having the above-mentioned defects had to be used for delay lines of less than 1 nS rise time.